Dave Fawbert says he wasn’t alarmed when he came across a boa constrictor on a high street in east London after popping out to buy a loaf of bread. It wasn’t moving, but the head of a pigeon was disappearing within the snake’s coils. “If it had been slithering around, I’d be more freaked out because you don’t know what it’s going to do,” says Fawbert, an editor at Shortlist.com, who posted a picture of the gruesome scene on Twitter on Saturday. “I wasn’t scared because it was quite obviously motionless – the bird was halfway down its throat and I thought: ‘There’s no way that snake’s going anywhere.’”

A couple of other people had stopped, so he asked if anyone knew where it had come from. “No one seemed to know. It was completely without explanation.” A crowd gathered. One person prodded it. “I just said: ‘Leave it, it’s not a danger to anyone.’” Except to the pigeon, he adds. Fawbert, who had been on a snake-handling experience day earlier in the year for his birthday (“I quite like snakes”), called the RSPCA, worried that people would be scared and try to kill it.

This seems to be turning into the summer of escaped snakes. Just over a week ago, a 2.4-metre (8ft) python was discovered in a man’s bathroom in Exeter after he heard toiletries and his toothbrush crashing to the floor, and went to investigate. Stuart Saunders, who is visually impaired, tried to pick up the strange tubular shape on the floor, thinking it was a piece of insulation that had fallen from somewhere, and realised it was a huge snake. He called a friend to help deal with it; the python was rescued by a nearby exotic pet shop. It is thought it escaped from there and somehow made it to Saunders’ flat through the plumbing.

A few days earlier, a woman in Kensington, west London, woke up to find a 1-metre (3ft) royal python curled up in bed next to her. An RSPCA officer, Jill Sanders, caught it the next evening – it had slithered off and was hiding in the flat. It was thought to be an escaped pet. “Reptiles, particularly snakes, can be extremely good escape artists and will take the opportunity of a gap in an enclosure door or a loose-fitting lid,” Sanders says.

Before a race in Battersea Park, south-west London, last week, a snake, thought to be a baby boa constrictor, was found by a runner who had gone into the bushes to relieve himself. The organisers put it in a large plastic tub, says Kate Carter, the Guardian’s life & style editor, who was running that day. “They covered it up a bit with a hi-vis bib because someone who seemed to know about snakes thought it was exotic and could be cold, even in heatwave London. They looked after it and called the RSPCA, who came to collect it.”

In May, the Manchester Evening News reported that Cordelia, a royal python – thought to be pregnant – had escaped from her home in Wythenshawe. “In the day, she just roams around my flat,” said her owner. “They are very intelligent creatures – which is what makes them good escapists as well. People have suggested Cordelia could still be in the flat somewhere, but I think she’ll have gone for a wander round.”

It is still too early to say if the number of stray snakes reported this year will be higher than previous years, but they are more likely to be reported in the summer. “There are a couple of theories why this is happening,” says Nicola White, the senior scientific officer for exotics at the RSPCA. Some snakes may have escaped months ago and haven’t been as active during colder weather, “maybe lying dormant somewhere. Then as soon as the warmer weather starts, they come out because they’re more active naturally in heat. The other reason we think there may be more escapees in summer is that there are owners who like to take their snakes outside to enjoy the warmer weather. In theory, it’s a good thing to do – it’s good for an animal to get natural light, natural warmth – but we would discourage anybody from doing that without keeping the snake secure. The problem is they warm up and become quite fast, and that’s when they could escape.”

White says we should not be unduly alarmed by stray snakes. “There are some species that are venomous,” she says. “There are also larger snakes that could be potentially dangerous if not handled correctly. In an RSPCA centre, when we have a snake over a certain size we have [to have] one person per metre of snake because that snake is quite powerful. It has the potential to wrap around [a person] and constrict.” But normally, the snakes they are called about are not dangerous – most are corn snakes, which grow to around 1.5 metres.

The python in Stuart Saunders’ bathroom. Photograph: DevonLive.com

What should you do if you spot a stray snake? White says you should call the RSPCA. “Our advice is always to keep a safe distance – don’t try to collect the snake yourself, or touch it. Just monitor it so we know where it is.” An officer trained in handling exotic animals will attend – for a standard-size boa constrictor, say, one person can catch it. They carry an “exotics kit”, which consists of a snake hook and a bag that can be tied at the top, and they are taught how to collect the snake safely, using the hook to control the head and gently lift it. To collect a very large snake, such as a reticulated python, which can grow to about 6.5 metres (21ft), two officers would be needed. “For one thing, they’re very heavy,” says White. If a venomous snake is on the loose, a specialist will be brought in.

Some snakes will have been abandoned, particularly by people who didn’t realise what they were taking on as a pet. “Before going out and buying a reptile on a whim, we’re desperately asking people to do their research – how long is it going to live for, and how are you going to look after it properly?” But as snakes are good at escaping, “We don’t think all the ones we’re picking up have been dumped or abandoned – it’s quite likely a lot of them are escapees.” Snakes can be microchipped, but many aren’t and reuniting them with their owners is very difficult.

There are thought to be about 2 million snakes kept as pets in the UK; corn snakes and royal pythons are the most popular species. Are they becoming more popular? “They’re a very convenient pet,” says Chris Newman, the chair of the Federation of British Herpetologists (FBH). “You don’t have to feed them every day, you don’t take them for a walk. For people with busy lifestyles, reptiles are becoming a replacement [for a cat or dog].” Newman keeps about 100 snakes, after getting his first when he was five. What’s the appeal? “I just find them fascinating,” he says.

Venomous snakes are very uncommon as pets – you need a licence to keep one. A survey by the FBH found about 60 people in England had licences, keeping about 300 venomous snakes in total. In 2011, a breeder in Nottinghamshire died after being bitten by one of his king cobras. Earlier this year, a coroner ruled that a man in Hampshire had probably been killed by his 2.4-metre African rock python, which he had kept as a pet since she was a baby, along with nine other snakes. It is thought the snake coiled around Dan Brandon’s body, asphyxiating him in August last year. Newman, who now looks after this snake, is dubious of the coroner’s findings, but even if the snake did kill its owner, these two deaths are exceedingly rare. “I’ll never say they’re not dangerous, but I always say there are roughly the same number of dogs as there are reptiles,” says Newman. “Dogs kill between three and seven people every year, and for reptiles we’ve had two deaths in 100 years. [But] I wouldn’t advise anyone to keep a large constrictor or venomous snakes without thinking it through.”

The public are not particularly at risk, although Newman thinks our long, hot summer will mean more escapees than usual. “We pick a lot of these animals up and you can almost guarantee that if you get a phone call from someone who has found a snake in their garden, it will be the neighbour’s. It’s not an absolute rule, but almost certainly within three doors away you’ll find where it came from.”

How far can they move? “They can move fast in short bursts, so they can disappear quite quickly. They’re wanderers, so they will move until they find somewhere they feel comfortable and secure. They could come from next door, find your bathroom and stay there, as long as there’s food. If there isn’t food, they will move again.” Typically, they will feed once a week, or every two or three weeks. “If there’s not any food, not any mice or anything like that, they will move. They can travel quite a long distance, there’s no limit.” A python or boa constrictor could survive outside at this time of year, but will die during the first frost. “Some of the north American snakes can survive our winters,” says Newman. “It’s not uncommon for a corn snake to escape in the autumn and be found in the spring.”

Last year, sewage treatment workers in Llanllyfni, Gwynedd, found a corn snake that had escaped – down the toilet – from a house four months previously and reunited it with the owners. In Glasgow, another corn snake was discovered living in the body work of a Transit van its owner had hired to move house five months earlier – it had wriggled free from its bag and box while being transported. The snake was discovered slithering between the seats by someone else who hired the van.

In July, Jake, a 1-metre kingsnake, escaped from his vivarium, probably after breaking out through a small vent. His owner, George Mole, had gone away for a few days, leaving his pet snake – one of three – digesting a frozen chick at home in Nailsworth, Gloucestershire. Jake was found a month later, about half a mile from home, after Mole put a post on a local group on Facebook. “It was a bit of a miracle. I think overjoyed is an understatement,” he says, about being reunited. Though he adds that the 14-year-old whose birthday party Jake crashed didn’t feel quite the same. The party, says Mole, “ended up in lots of screaming”.